Method for modifying wheat gluten



Patented Jan. 22, 1952 eta iiiemmno was John Resales-alien, St. Pauli Minn assailant General Mills, Inc., a corporation of pelawarep No Drawing. Application September- 9, a I V Serial No. 114,923

The present inventionrelates-to a novel wheat lu pre ue and a proeesso ep epa ne it.

h at l en n. the pr sence o wa r b l V 7 Claims. (01. 260-112) ws to ve ti td u h irn sa which. isle rateris 1 this-p cte n h ch idi t neuis esl' it t m- .Qb comm qi rq e ns and srhichu,

prevents it from being usefnljn the applications: in whi er ommereiaro e a e u eil ih pr sent. inv n n latesta awheats uten uc w i h ha Vibe o ified i om the e ural characteristics of gluten, such that it is" Lib in the range of 145-155;CQ-preIerably at 150 0.

and for a time period within the approximate range of 15-60 minutes-,'preferably -30 minutes. While the amount of water' presentduring the hydrolysis is not critical, it is --usually found desirable to operate in an aqueous-medium in which the gluten centration.

- The exact nature of thereactlonwhich takes? place is not definitely-understood but-itinvolves a partial hydrolysis of thegluten. Thisvis eviuseful innumerous ways;in which theunmodi fied gluten is without utility; Thus,;f or example; the, V modified gluten of the present invention has been found to headmirably suited for-useas an adhesive and for the stabilization of natural and? synthetic rubber latices, uses to which unmodified gluten cannot be put.

The modified wheat gluten ol f'the present ini vention is obtained by;; a limited hydrolysis ,Of

the gluten in an aqueous inediumcontaining an alkaline earth metal oxide such as calcium oxide; in which the hydrolysis'is carried out-under 'carefully controlled conditions within a restricted rangi 7 l- V.

There are numerousreports in the literature of the hydrolysis {of-proteins including'gluten: However the hydrolysisof gluten under-the eon di'tions herein described-and-the;productionof amodified gluten producthaving the propertie described is entirely new; -'-I he-produc-t-thus ob-- characteristics of the unmodii'ied gluten and demonstrates water solubility. over the entire pH range; The product isalso; soluble -in--various"" aqueous-organic solvent mixtures, such as 60-70% alcohol or ethylene glycol-nionomethyl ether (methyl Gellosolve),.- Theproduct is an excellent remoistening adhesive having high bond strength, quick grab, and simplicitymtapplicw tion. :Ll-t is a so usefu as. a pr t t e co loi in stabilizing; natural-and synthetic rubber latices It isthereforean object of ,the presentinven tion to provide; a novel-lime hydrolyzed-gluten,

and to provide a process of producingltheufiame 1 The hydrolysis of th denced by an increase: in the amino; nitrogen content and by adecrease inxthe amide nitrogen content. This is indicative that amide or peptide bonds are being hydrolyzed, resulting'inproducts of shorter: chaine-tlengthw:"Theehydrolyzed prodnot also demonstrates a reduced which 15-, the stain itetoeiyliamaed" lay concentration. This reduction in the is indicative of a reduction in the average chain length of the polymers in accordance with known 1 polymer chemistry. 1; a: t While there is some variation possible in the hydrolysis conditions as pointed out above; these hydrolysis conditions in general produce similar tained no longer possesses -the--elastic 'dougl1y of m fl following table will show calcium oxide concentration and at a fixed temperature. n L

Degree of hydrolysis wheat o'luten with s-t9 t m at Gluten ,-Dis"persed.i l 1 as Per cent of --Original- Gluten ease is at approximately 20% 0on 3 The effect of variation in time of hydrolysis upon the nitrogen distribution and on is shown by the following table:

TABLE II Characteristics of gluten hydrolyzed at 150 C.

using CaO as 3% of dry gluten weight for various time periods Nitrogen Distribution as Per Time of cent of Total Nitrogen Specific Hydrolysis Viscosity Min. Concentration Amino Ammonium Amide The effect of variations in calcium oxide concentration upon nitrogen distribution and on is shown by the following table:

TABLE III Characteristics of gluten hydrolyzed for 30 min. at 150 C. in presence of varying quantities of calcium oxide Nitrogen Distribution as Per gint g? Cent of Total Nitrogen specific viscesity Gluten Concentration Amino Ammonium Amide The products of the present invention are all very soluble and moreover, demonstrate gluten solubility over the entire pH range, having a minimum solubility of around pH 4-5. The following table will show the dispersibility of the various lime hydrolyzed glutens with variations both in the amount of lime used for the hydrolysis, as well as variations in the pH of the aqueous solution in which the hydrolyzed glutens are dispersed:

TABLE IV This table shows that even at the point of least solubility of around pH 4-5, there is a solubility of from 60-75%. At a pH of 7 or higher, and at a pH of 3 or lower the materials are almost completely soluble. The high degree of solubility at a neutral pH is of considerable interest and value for commercial uses where neutral solutions are desired. Moreover, the high solubility in the acid range may be of value where acidified adhesives are used on metal foils.

As was pointed out previously the products of the present invention demonstrate good solubility in such organic solvents as aqueous ethanol and in aqueous ethylene glycol monomethyl ether. The following table demonstrates the solubility of gluten which was hydrolyzed with 3% calcium oxide at 150 C. for 30 minutes, with variation in the pH of the aqueous ethanol as well as variations in the concentration of the ethanol.

TABLE V Dispersibility of CaO hydrolyzed gluten in aqueous ethanol Nitrogen Dispersed as Per Cent Ethanol Cone. of Total Nitrogen Per Cent By Weight 'pl'lfi DHS The alcohol dispersibility of the modified gluten makes the material well suited for application to oily surfaces. The presence of the alcohol permits the oil film to be displaced and the protein adhesive to contact the bare surface. Not only is the original modified gluten dispersible in aqueous alcohol, but also gummed tapes or labels may be remoistened by the aqueous ethanol.

The adhesive qualities of calcium oxide hydrolyzed glutens were tested in the following manner: Gluten was hydrolyzed for 30 minutes at C. in the presence of 2%, 3%, 4% and 5% calcium oxide. Since there exists no general adhesive test giving-numerical values acceptable to various industries, a relative test of the various calcium oxide hydrolyzed glutens was carried out as follows: Strips of 90# kraft paper were coated with 10% aqueous solution (pH 7) of the various CaO gluten preparations. After drying, the strips were out to a width of 0.5 inch. One strip was immersed in water for 2-3 seconds, then placed on a dry strip so that the coated surfaces overlapped 0.5 inch. The resulting bond was allowed to dry under a constant weight. The strips were then held at one end by a stationary clamp while an empty container was fastened to the other end. Into this container there was poured lead shot until the weight caused either the paper or bond to rupture. The results of these tests are presented in the following table:

TABLE VI Bond strengths of calcium oxide gluten, casein, and animal glue Since the paper ruptured in all instances the lime hydrolyzed gluten preparations were certainly the ql l the other proteins in this application.

gluten to be absorbed'by the paper was not en--- in excessnflow is" reduired'- in =order tdtavoid undue absorption of the gluten by the papers Hydrolyaed gluten having an:

of less than' 7-.08aisfcapab1'e of tusein sti engthenins i the paperzitself. i

Blocking tests weremrun 'on zpiasticized': and" non-nlastici'zed lime sli-ydrolyzed gluten"icoatings; and it 'was fonnd'ith'at-the anon-plasticized gluten coatings demonstrated; 'no' tendencytoward bloclti'ngi '1- It was ialsowfoundsthat ethylene 'glycol a monobutyl ether;v (butyl Cellosolve) and that" sorbitan -monolaur'ate' polyoxyalkylene "derivative (Tween )'*-could bei'used' as plasticizers for'icais cium' oxide hydrolyzed gluten coatings; These tests were run by preparing a'BO dispersion ofthe li m'e hydrolyzedxgluten' in wate'r and adjustand the solution; spread- =on'2 #"'kra'ft" tape: Thereafter theyf were: dried and the blocking tests'were run according to the: A: S:- T. M: standard at" 75% relatives-humidity and "at a temperature "of-1 37-38 C; The plasticizers were employed in a concentration. of 10% based: on the weight 'of'the protein;

These proteifiproducts were also tried "aspro; tective colloids for-natural and synthetic rubber laticesfi "Naturalrubberlatexis quite-unstablev to mechanicalagitationi' For this reasoni-scme protective colloid, such as' casein; is usually used by pumps 'Withmli'cbagljlltiOl'lp A comparison was made of thei e'fiect 'oijlime-hydrolyzed gluten and caseini uponitheistability-ofithe rubber latex. When both proteins were made into 5% dispersions and added to the 'rubber latexin concentrations etude-2.0% of .-the-dryrubber solidsythei lime hydrolyzed gluten was found to stabilize-the. latex for longer periods of time than. thecasein.

solution wai's' about as high ai concentratiori as could'i'b'e addeds-to the latex an'dis'till obtain gooa mixing' prior to: the agitati'on testw inf contrast;

a 50% solution oi lime-hydrolyzed. gluten could be added to the latexandgbcd mixing obtained for the agitation test. A comparison of the 15% i V B moval'", of fat froni gthe gluten. Wheat gluten comn'iei'ciallifavailable'on the market may con :tainseveral percentoi fat which has accompanie'd'thlgluten from thel fldlll from which the calcium oxide and; the" y the free fatty the calciu ber latex d'des 0t have to be di-luted as" much -as fi when casein is employed' for -this purpose: *It has also beer'i iound that the limehydrolyzed "gluten of the present ir' yention isas effective as caseimf r stabilizing syntheticlatices in starch clay'jjeoatingfcompositions: In this application; a 1 it again, iijoy's the propertyof ready solubility ntjent"solutions in cold water.

ids "content solutions may be added ldiiectly'to, the 'synthetic latices with only slight increase inf'vijscosijtyg' In contrast to these properties;,caseinjcan be" used only for the-pro-. T *ductio' or; relatiyelyjlow concentration solutions ."solutio'ns itend-[fodun'duly increase the L of thisy the 'd-l As to,all-{of th e applications; 'the lime hydroly'zedjgluten ca1ciulno'Xide fcontailied 59% of "fat based an fl form; calcium soaps whi'ch may be filtered off; oifcentrifugedofi; These soaps may then be use'd"to"'work"up free fatty acids -At the same time, the removalfoffthe soaps results' an; eggc'ellentfprotein product;

The following examples will serve to illustrate the invention:

E A P E- 1 H Sixvhundred grams of freshly washed-gluten v v y if was placeda imai-mixen while-beingagitated to stabilize. the.latex-.so--that itsmay be handled 3,6.3 gsilqfi%caouriwaszlmfimately mixewithfi the gluten until a homogeneoiis mass wa's obminutes Therewas tlidn added slowl' bvewa'petiod of 1-5. minutes, n. s'total Oi 39.0 gof? water; and mixing was tained. This required about continue unt k hoinogeneoussfluid masswas obtainidi- "ThisAast; mixing' period "required anproximately 153; m-in-u'tes'.= The -resulting mixture hadthe following composition mediately chilled in water. To the contents of I the bomb there was added 0.9 g. of ammonium 1 y In one"experiinentjtwo *sam es;o gmtenwe'r'e"hydrolyze at C'ffor d'jminutesj one inthe' presence 0'1 1 y N ther inthe presence of 3% dfcalciliiii j'0Xide.'""A-fter"the hydrolysis it. was fodnd'ithatthe'SamDle hydrolyzed with"1% the weightbfjthfe dispersed product, whereas the other 'sampl fat iri"thejbrocess"'is apparently-hydrolyzed to idsjjwhich 'tnencombine with 3% ofdrygluten weight" The iiuid alka-line gluten (pl-112,4) was introduced into, a; stainless-asteel bomb, then auto-- clavedz-atflflt steam: pressure for-3O minutes. At

the end, o i the hea ting periodthe-bomh was 'imaceaoes 7 the wash water was combined with the supernatant. The whole was then filtered through filter paper pulp and filter aid on a Buchner funnel. drum dried at 60-85# steam pressure.

EXAMPLE 2 Calcium oxide equal to 3% of the dry weight of gluten (1% wet weight) was added and the material mixed until a smooth homogeneous mass was obtained. Sufficient water was slowly added to lower the protein concentration to 20%. During the addition of water, agitation was continued so that a lump-free homogeneous mass was obtained. This fluid alkaline gluten was then introduced into an autoclave fitted with a stirrer and the gluten was hydrolyzed at '70# steam pressure for 30 minutes. The hydrolysate was The resulting clear tan-coloredfiltrate was;

then blown ofi into a holding tank. The hot hydrolysate after being passed through a watercooled coil was mixed with a solution of ammonium carbonate. The material was then passed through a solid bowl centrifuge which removed the precipitated residue. The centrifugate containing approximately 15-20% solids was concentrated in a vacuum evaporator to 45% solids concentration. The resulting viscous sirup was then dried on a drum drier at 60# steam pressure.

In large scale operations carbon dioxide may be used in place of the ammonium carbonate to precipitate excess calcium. Ammonium carbonof the gluten, heating the reaction mixture to a temperature within the approximate range of 145-155" C. for a period within the approximate range of 15-60 minutes.

8. Process of modifying wheat gluten which comprises reacting wheat gluten in an aqueous medium with lime, the lime being employed in a quantity of 3% based on the dry weight of the gluten, heating the reaction mixture to a temperature within the approximate range of 145- 155 C. for a period of approximately -30 minutes.

4. Process of modifying wheat gluten which comprises reacting wheat gluten in an aqueous medium with lime, the lime being employed in a quantity of from 2-5% based on the dry weight of the gluten, heating the reaction mixture to a temperature within the approximate range of 145-155" C. for a period within the approximate range of 15-60 minutes, precipitating excess soluble calcium, and removing the precipitated calcium.

5. Process of modifying wheat gluten which comprises reacting wheat gluten in an aqueous medium with lime, the lime being employed in ate, however, is convenient for small size operations. In the preparation of an adhesive from lime hydrolyzed gluten prepared from a fat-free or low fat gluten, it is unnecessary to remove precipitated material, and it is possible to simply dry the hydrolysate. Where the gluten employed contains a large amount of fat it is preferred to remove at least part of the precipitated-calcium soaps and calcium carbonate. In the preparation of a high quality protein, however, such as is used in the stabilization of natural and synthetic latices, it is desirable to precipitate the excess calcium and to remove it either by filtration or by centrifugation. 1

While the invention has been described with particular reference to calcium oxide, other alkaline earth oxides such as magnesium oxide, are

productive of similar results when used in the same quantities as the calcium oxide.

While various modifications of the invention have been described, it is to be understood that other variations are possible without departing from the spirit thereof.

I claim as my invention:

1. Process of modifying wheat gluten which comprises reacting wheat gluten in an aqueous medium with an alkaline earth metal oxide, the alkaline earth metal oxide being employed in a quantity of from 2-5% based on the dry weight of the gluten, heating the reaction mixture to a temperature within the approximate range of 145-155" C. for a period within the approximate range of 15-60 minutes.

2. Process of modifying wheat gluten which comprises reacting wheat gluten in an aqueous medium with lime, the lime being employed in a quantity of from 2-5% based on the dry weight a quantity of from 2-5% based on the dry weight of the gluten, heating the reaction mixture to a temperature within the approximate range of -155" C. for a period within the approximate range of 15-60 minutes, precipitating the excess soluble calcium ions as the carbonate, and removing the precipitated calcium carbonate.

6. Process of modifying Wheat gluten which comprises preparing an aqueous dispersion of gluten at about a 20% concentration and containing lime in the approximate proportion of about 3% by weight of the dry weight of the gluten, heating the aqueous dispersion to a temperature within the approximate range of 145- C. for a time period within the approximate range of 15-60 minutes, precipitating excess calcium as the carbonate, and removing the precipitated carbonate.

7. Process of modifying wheat gluten which comprises preparing an aqueous dispersion of gluten at about a 20% concentration and containing lime in the approximate proportion of about 3% by weight of the dry weight of the gluten, heating the aqueous dispersion to a temperature within the approximate range of 145- 155 C. for a time period within the approximate range of 15-60 minutes, precipitating excess calcium as the carbonate, centrifuging the dispersion'to remove precipitated calcium carbonate, and drying the centrifuged disperesion.

JOHN ROBERT COFF'MAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. PROCESS OF MODIFYING WHEAT GLUTEN WHICH COMPRISES REACTING WHEAT GLUTEN IN AN AQUEOUS MEDIUM WITH AN ALKALINE EARTH METAL OXIDE, THE ALKALINE EARTH METAL OXIDE BEING EMPLOYED IN A QUANTITY OF FROM 2-5% BASED ON THE DRY WEIGHT OF THE GLUTEN, HEATING THE REACTION MIXTURE TO A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 145-155* C. FOR A PERIOD WITHIN THE APPROXIMATE RANGE OF 15-60 MINUTES. 